The main objective of this project is to provide a research resource (the Chemobyl Tissue Bank: CTB) for both ongoing and future studies of the health consequences of the Chemobyl accident. It seeks to maximise the amount of informationobtained from small pieces of tumour by providing multiple aliquots of RNA and DNA extracted from well documented pathologicalspecimens to a number of researchers world-wide and to conserve this valuable material for future generations of scientists. It exists to promote collaborative, rather than competitive, research on a limited biologicalresource. The CTB ensures that the best possible diagnosticservice is provided to patients and that appropriate ethical consent is obtained for each biologicalsample, that specimens are properlydocumented and sampled and that biological materials are available for appropriate research studies. A diagnosis for each sample, agreed by internationally recognised pathologists,is made available to research groups carrying out molecular biological, therapeutic, epidemiological and other studies. The C'rB provides an archive of research data generated from research studies carried out usingthe resource material. This data may have direct relevance to both prognosisand assessment of riskfrom exposure to radioactive fallout from a nuclear accident. The CTB allows multiple researchers access to the same material, permittingcomparison of different techniques for the same molecular marker and analysis of multiple molecular markers. It provides the opportunity for additional markers (as yet unknown) to be studied in the future. A number of similar projects to amass biologicalarchives from specific patient groups exist. However, few of these projects seek, from their outset, to collate research data produced fromthe samples collected. This archive is different inthat it deals with a relatively rare tumourwhose aetiology is known (exposure to radioiodine in fallout), therefore enabling study of the interactionof environment and physiology,it is highly likelythat many of the mechanisms involved inthyroid carcinogenesisare common to other cancers. The research supportedby this resource may therefore have other benefits to the treatment of cancers in other tissues.